Acta Chimica Sinica ›› 2020, Vol. 78 ›› Issue (7): 680-687.DOI: 10.6023/A20030097 Previous Articles     Next Articles



曹洪涛a, 李波a, 万俊a, 余涛a, 解令海a, 孙辰b, 刘玉玉a, 王锦a, 黄维a,c   

  1. a 南京邮电大学信息材料与纳米技术研究院 有机电子与信息显示国家重点实验室培育基地 南京 210023;
    b 西班牙马德里高等研究中心纳米研究所 马德里 28049;
    c 西北工业大学柔性电子前沿科学中心 西安 710072
  • 投稿日期:2020-03-31 发布日期:2020-06-04
  • 通讯作者: 解令海, 刘玉玉, 黄维;;
  • 基金资助:

Cyano-substituted Spiro[fluorine-9,9'-xanthene] Derivatives: Exciplex Emission and Property Manipulation

Cao Hongtaoa, Li Boa, Wan Juna, Yu Taoa, Xie Linghaia, Sun Chenb, Liu Yuyua, Wang Jina, Huang Weia,c   

  1. a Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications (NUPT), Nanjing 210023, China;
    b Madrid Institute for Advanced Studies in Nanoscience, IMDEA Nanociencia Calle Faraday 9, Ciudad Universitaria de Cantoblanco 28049, Spain;
    c Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an 710072, China
  • Received:2020-03-31 Published:2020-06-04
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Nos. 61605090, 61604081, 61604076, 21774061, 91833306), the Natural Science Foundation of Jiangsu Province (BK20190090, BK20180751), the Six Peak Talents Foundation of Jiangsu Province (XCL-CXTD-009) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, YX030003).

Thermally activated delayed fluorescence (TADF) molecules have great potential in developing organic light-emitting diodes (OLEDs) because of their efficient emission and low price. Compared to pure-molecules, exciplex systems are drawing much attention since they can realize small singlet-triplet energy splitting (ΔEST) more easily for TADF. However, the species and molecular design systems of electron-acceptors for exciplex-TADF are still limited even though some acceptors have been reported. In addition, the relationship between TADF properties and the structures of acceptors requires further investigations. Herein, we report the design and synthesis of two novel spiro[fluorine-9,9'-xanthene]-based acceptors (CNSFDBX and DCNSFDBX) for achieving exciplex-emissions by using tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as a donor. The photoluminescence measurements suggest that both of the doping-systems (TCTA:CNSFDBX and TCTA:DCNSFDBX) possess exciplex emissions. Whereas, it is observed that the TCTA:DCNSFDBX system displays higher photoluminescence quantum yield and electroluminescence efficiency than TCTA:CNSFDBX. For better explaining this phenomenon, we perform low-temperature fluorescence and phosphorescence spectra investigations. The experimental results show that the TCTA:DCNSFDBX system exhibits smaller ΔEST values (0.12 eV) than TCTA:CNSFDBX (0.46 eV). This results indicate that the reverse intersystem crossing from non-radiative triplet states (T1) to radiative singlet states (S1) and TADF processes can be realized more easily in the TCTA:DCNSFDBX system. Moreover, the electrochemical measurements and theoretical calculations suggest that the lowest unoccupied molecular orbital (LUMO) level of DCNSFDBX (-2.86 eV) is lower than that of CNSFDBX (-2.47 eV). This situation implies that DCNSFDBX possesses stronger electron-accepting ability than CNSFDBX with the help of dicyano-substitution. Furthermore, the TCTA:DCNSFDBX system displays larger driving force (0.39 eV) than TCTA:CNSFDBX (0.22 eV) in their exciplex-formation processes, suggesting the exciplex-emission (TCTA:DCNSFDBX) can be achieved more easily. Therefore, the higher exciplex-emission efficiencies of the TCTA:DCNSFDBX system are attributed to the stronger electron-acceptability of DCNSFDBX through dicyano- substitution and larger driving force in its exciplex emission process. This work provides a route to further development of new electron-acceptors for exciplex-TADF.

Key words: spiro[fluorine-9,9'-xanthene], exciplex emission, thermally activated delayed fluorescence, steric hindrance, cyano-substitution